A motor converts an electric energy into a kinetic energy. The motor is divided into a rotary motor for converting an electric energy into a rotary movement force, a reciprocating motor for converting an electric energy into a linear reciprocation force, and etc.
FIG. 1 shows one example of the reciprocating motor. As shown, the reciprocating motor comprises: a stator composed of an outer core 100 and an inner core 200 inserted into the outer core 100; and a mover 300 movably inserted between the outer core 100 and the inner core 200 of the stator.
The mover 300 includes: a magnet holder 310 formed as a cylindrical shape and inserted between the outer core 100 and the inner ore 200; and a permanent magnet 320 coupled to the magnet holder 310.
A winding oil 400 and a bobbin 410 where the winding coil 400 is positioned are coupled to inside of the outer ore 100. The bobbin 410 is formed as a ring shape, and the winding coil 400 is formed accordingly as a wire is wound on the bobbin 410 several times. The bobbin 410 and the winding coil 400 can be coupled to the inner core 200.
The outer core 100 is formed as a cylindrical shape having an inner diameter of a certain size, and has a certain width. A sectional surface of the outer core 100 in a circumferential direction thereof is composed of an opening groove 110 inwardly open so that the winding coil 400 and the bobbin 410 can be located; a pass portion 120 corresponding to an outer side of the opening groove 110 for passing a flux; and a pole portion 130 corresponding to both ends of inside of the pass portion 120 for forming a pole.
The inner core 200 is formed as a cylindrical shape having a certain width. A sectional surface of the inner core 200 in a circumferential direction has a quadrangular shape having a certain width and length.
The unexplained reference numeral R denotes a fixing ring.
Operation of the reciprocating motor will be explained as follows.
As a power is supplied to the reciprocating motor, a current is applied to the winding coil 400. By the current, a flux is formed around the winding coil 400. The flux forms a closed loop along the pass portion 120 of the outer core and the inner core 200.
The flux formed at the pass portion 120 of the outer core and the inner core 200 interacts with a flux formed by the permanent magnet 310 of the mover, so that a force is applied to the permanent magnet 310 in an axial direction. By the force applied to the permanent 310, the mover moves in the axial direction. If a direction of the current applied to the winding coil 400 is alternated, the mover 300 linearly reciprocates.
The outer core 100 and the inner core 200 constituting the stator S have various shapes and fabrication methods. The outer core 100 and the inner core 200 of the stator are fabricated by stacking a plurality of thin plates having a predetermined shape in order to minimize a flux loss. If the outer core 100 or the inner core 200 is one body not a lamination assembly, a flux loss is generated by a copper loss.
FIG. 2 is a disassembled perspective view showing one example of the inner core of reciprocating motor.
As shown, the inner core 200 of the reciprocating motor is a cylindrical lamination assembly formed accordingly as quadrangular lamination sheets IS having a certain thickness are stacked as a cylindrical shape. The lamination sheets IS are stacked so that relatively long side edges 1 can be positioned at an inner circumferential side and at an outer circumferential side of the cylindrical lamination assembly. An opened groove 3 is formed at both short side edges 2 of each lamination sheet. By the grooves 3, a ring groove 210 is respectively formed at both side surfaces of the cylindrical lamination assembly. The fixing ring R of a ring shape is respectively coupled to the ring grooves 210, thereby fixing the lamination sheets IS.
The outer core 100 of the reciprocating motor is constricted as the same shape as the inner core. That is, the outer core 100 is formed accordingly as lamination sheets of a predetermined shape are stacked as a cylindrical shape. The lamination sheets are radially positioned toward the center of the cylindrical lamination assembly.
However, in the stator of the reciprocating motor, that is, in the outer core 100 and the inner core 200 constricted as a cylindrical lamination assembly, a volume occupied by the lamination sheets is less in a unit volume of the cylindrical lamination assembly. According to this, a flux density is relatively high at the time of forming a flux thus to increase a flux resistance. More specifically, as shown in FIG. 3, since the inner core 200 is constructed as a cylindrical lamination assembly that the lamination sheets IS having a certain thickness are stacked as a cylindrical shape, a dense state between adjacent lamination sheets IS is maintained at an inner circumferential surface side of the cylindrical lamination assembly. However, at an outer circumferential surface side of the cylindrical lamination assembly, an interval h between the lamination sheets IS is formed. The interval h between the lamination sheets IS is increased with a certain ratio towards the outer circumferential surface side from the inner circumferential surface side of the cylindrical lamination assembly. In case that the outer core 100 is constructed as a cylindrical lamination assembly, the above explanation is also applied.
According to this, much space is formed in the cylindrical lamination assembly, so that a volume occupied by the lamination sheets IS is less in the unit space of the cylindrical lamination assembly. Therefore, a flux path becomes narrow thus to increase a flux resistance and thereby to lower a motor efficiency.